1. Field of the Invention
The present invention is broadly concerned with novel, low cost cheese starter media which can be used by cheese makers in the growth of bulk starter cultures, along with a unique method of producing the media. More particularly, it is concerned with such media which in preferred forms include a minor amount of free or unbound lecithin, and/or minor quantities of sodium tetraphosphate for purposes of imparting a stable, homogeneous disperson of the starter media ingredients; in its method aspects, the invention involves preparation of a liquid preblend including phosphate anti-bacteriophage agent(s) and, preferably, lecithin, and mixing of the preblend with milk-derived nutrients (e.g., whey and nonfat milk), followed by drying to yield a smooth, consistent, substantially uniform and homogeneous reconstitutable powder.
2. Description of the Prior Art
In the manufacture of natural cheese, milk in a cheese vat is inoculated with a minor amount (e.g. 2-4 percent) of a bulk starter providing the necessary culture of acid-forming microorganisms used for the particular cheese being manufactured. For example, in the case of Italian cheeses such as mozzarella, it is the usual practice to employ Streptococcus thermophilus together with one or more lactobacilli such as Lactobacillus bulgaris. In the art, the streptococci are generally referred to by the short name of "coccus", while the lactobacilli are referred to as "rod" bacteria because of their appearance under microscopic examination.
The quantity and activity of cheese-making microorganisms can be critical to the overall outcome of the process and final cheese quality. Again referring to Italian cheese, it has been found that, in order to make acceptable cheese, the ratio of coccus to rod microorganisms in the starters should be from about 1:1 to 5:1, the most preferable level being about 2:1 to 3:1. If these ratio considerations are not met, the final Italian cheese product may be deficient in flavor or physical properties such as elasticity and "stringiness."
It is the universal practice among cheese makers to grow their bulk starters using relatively minor amounts of seed culture. In such techniques, the seed culture is inoculated into a starter medium and allowed to incubate therein so that the culture cells will multiply to produce the desired bulk starter for use in cheese making. Here again, the types of starter media and the techniques used during the incubation process can have a relatively critical outcome on the quality of the final bulk starter, and hence on the cheese ultimately produced. A dilute dispersion of nonfat milk (e.g., 12 percent slids level) in water has long been considered the starter medium of choice. However, use of nonfat milk in this context is a relatively expensive proposition, and therefore cheese makers have in the past sought to use media of a less expensive nature which either eliminate nonfat milk entirely, or sharply limit its use by provision of substitute materials.
For example, U.S. Pat. No. 3,852,158 describes a starter media which includes milk-derived materials, a nitrogen source, and citrate anion. In preferred forms, the starter media described in this patent contain a major amount of sweet whey and a minor amount of nonfat dry milk solids.
U.S. Pat. No. 3,998,700 describes starter media which include both acid and sweet whey solids together with nonfat dry milk solids. Finally, U.S. Pat. No. 2,805,950 describes the use of whey for culturing bacterial microorganisms used in making a swiss cheese.
While a number of alternative starter media have thus been proposed in an attempt to provide an acceptable substitute for expensive nonfat milk, none of these media have given results completely equivalent to that of the nonfat milk. In many cases, the alternative media do not provide the ideal environment for bacterial growth, or in the case of Italian cheese making, the final coccus to rod ratio obtained may be improper. Moreover, in those media which incorporate relatively large quantities of whey, a problem arises by virtue of the phenomenon known as "whey out." Specifically, large amounts of whey in a starter medium can precipitate to the bottom of the starter tank and create severe handling problems. In fact, these problems can become so severe that some cheese makers simply refuse to use starter media containing substantial amounts of whey, even if growth characteristics of such media are satisfactory.
U.S. Pat. No. 3,041,248 to Hargrove describes the use of various phosphates for the control of bacteriophage, which are active against lactic acid bacteria. Indeed, the many starter media presently available include various phosphates for the purpose of combatting bacteriophage. In this connection, it is known that the phosphates react with or tie up the readily available calcium ion present in the media, and this in turn prevents the bacteriophage from adsorbing onto the specific starter bacterium. In conventional practice, the phosphates are simply added directly to the remaining dry ingredients of a starter medium, followed by appropriate blending and bagging. This conventional dry blending procedure presents a number of practical problems in the use of starter medium, however, particularly with respect to the phosphate content thereof.
Specifically, the phosphates tend to be of irregular, grainy appearance and size in a dry condition, and therefore tend to settle out or stratify in the dry blended media. When the media are reconstituted in water, problems are presented not only from the standpoint of solubility (the conventional media are sometimes difficult to disperse in water), but more important the phosphates present may not completely react with free calcium ion. In order to ensure the most effective use of the phosphate anti-bacteriophage agents, it is desirable that the dry medium be smooth, uniform and substantially homogeneous; and this is particularly the case when it is borne in mind that the media may be used with radically different equipment and cheese-making practices from manufacturer to manufacturer. Non-uniformity inevitably means that in certain portions of the media the phosphate concentration is too low, while in other portions it is too high; and both of these conditions should be avoided.
In addition, when a typical dry blended powder medium is reconstituted in water, it is desirable to allow sufficient time for the phosphate to react with available calcium. Under normal cheese plant conditions, however, this reaction time should be minimized, and in some instances time constraints have forced cheese makers to employ a starter medium which has been insufficiently reacted; the result of this is that the problem of bacteriophage may not have been completely eliminated, and this in turn can have severe consequences in terms of cheese production.
In short, the irregular, non-uniform nature of many dry blended starter media compositions lead to a number of rather serious problems, most particularly with respect to the proper utilization of phosphate anti-bacteriophage agents present therein.
Accordingly, there is a heretofore unsatisfied need in the art for less expensive, alternative starter media, and a method of production thereof, which can be used in lieu of nonfat milk per se while giving essentially equivalent results in terms of culture growth and qualities, and which avoids practical difficulties such as "whey out" and problems stemming from non-uniformity.